There are a great number of video encoding applications. These include (list not exhaustive):                Digital TV transmission        Real-time video transmission on several types of networks: IP, mobile, (“Streaming IP”)        Computer storage of video        
The invention is applicable, in particular, within the framework of systems that implement MPEG-type encoding. MPEG-type encoding means encoding based on temporal prediction and discrete cosine transformation based on a hard block structure, often with a fixed size, but possibly with variable size. The two representative standards for this encoding family are the MPEG-4 standards of versions 1 to 4 and ITU-T/H.263 up to version 2. The invention can also be applied within the framework of the CCITT H26L recommendation (for example, see corresponding VCEG-N83d1 document).
The video encoding and decoding diagrams currently offered are divided into 2 categories:                Encoding standardised by either ISO/MPEG, or by ITU-T, all based on the same type of techniques (temporal prediction and discrete cosine transformation based on a block structure)        Encoding under development offered by research laboratories that invoke a large panel of techniques: wavelet encoding, regional encoding, fractal encoding, meshing encoding, etc.        
Currently, MPEG-4 encoding is considered the trade standard, not only in standardised encoding, but also in terms of published encoding.
MPEG-4 or ITU-T/H.263++ type encoding is considered as having reached its limitations, in particular due to the fixed-size hard block structure used as support for all encoding calculations and operations. In particular, the temporal prediction of images within a sequence is not sufficiently exploited.
Furthermore, published alternative encoding has not yet achieved a sufficient degree of optimisation.
Therefore, to allow encoded video sequences at low bit rates to be obtained, encoders normally reduce the size of images and create temporal subsamples of the original video sequence. Nevertheless, the second technique has the inconvenience of restoring erratic movements that are more or less problematic for the user depending on the subsample level.
To avoid these erratic movements, the missing images (unencoded) must be regenerated in the decoder using temporal interpolation.
Nevertheless, current techniques for the temporal interpolation of images do not allow satisfactory results to be obtained, particularly when they are implemented in a single decoder. Indeed, these techniques are the source of visual artefacts related to the movement compensation techniques based on blocks that only define a single movement vector for all the pixels of a block.
The purpose of the invention specifically is to remedy the limitations of previous techniques.
More precisely, one objective of the invention is to provide a technique for encoding and decoding image data, which allows a reduced bit rate and/or improved regenerated image quality to be obtained with respect to known techniques.